The subject matter of the invention is a system of vegetation strips for protection of slopes against erosion. This kind of protection is used with slopes with inclines ranging from 45.degree. to 65.degree.. The slope and also the space under the slope are efficiently protected against erosion and erosion materials. The vegetation strip system completely prevents erosion of the ground.
The technical problem, which is successfully solved with the present invention, is to retain erosion material on the slope, especially slopes with inclines exceeding 45.degree..
The known protections of slopes with inclines ranging from 45.degree. to 65.degree. are primarily made with dead materials--concrete walls etc. There also exist protective covers consisting of living vegetative material as the main active protective component and wire netting as a secondary but incomplete protection.
There are several drawbacks to protection of slopes by inorganic materials, e.g. a concrete wall. One drawback is limited life because the material used cannot regenerate. A second drawback is a technical problem posed by cascading mountain water which limits the height of protection. It has also proved impossible to achieve a protection that adheres to the main uneven configuration of the slope. Moreover there is the disadvantage of the additional space is needed at the foot of the slope for the foundation. This kind of protection is also ecologically inappropriate.
Among the protections applying living material there are also the so-called slope mesh and slope support. Slope meshes are of several types, depending on the inclination and the height of the slope. The basic principle of the mesh is to anchor the wooden or concrete mesh to the slope and then put earth into the openings of the mesh. The great volume of the filling material which covers the whole slope becomes a statical problem at a certain slope height. For that reason this kind of protection is appropriate for slopes with limited inclines. Wooden meshes are usually designed for slopes with inclines not exceeding 45.degree., although there exist special types intended for steeper slopes (intensive filling of vegetative material results in an increase of the angle of internal friction of the filling material), but this kind of protection is limited to heights ranging between 3 and 5 meters with slopes having an incline of 65.degree..
The concrete type mesh has similar and usually even greater disadvantages. This type is used for consolidation of the ground (slides) rather than for surface protection of steep excavated slopes.
A great disadvantage of all slope meshes is that they do not adhere well to uneven configurations, so their use is limited.
Slope support is used for protection of steep overhanging points but its application is also very limited.
Recently, slopes have been protected with wire or plastic netting. The protection is perfect only in slopes with small inclinations--only operative with in even slopes with inclinations of 60.degree. where the wire netting closely adheres to the slope, where there are not water sources and no large oscillations of daily temperatures (northern side) and where the slope does not contain moisture or is subject to freeze. In complex cases the wire netting is fixed by rock bolts to prevent separation of the netting and to hold the erosion material on the slope. However, the wash away of--especially--small fractions from the slope and constant movement of erosion material under the netting prevents the vegetation cover from developing. On soft slopes, the rock bolts get loose under the pressure of the material accumulated under the netting, so this material slides down the slope, devastating the already growing protection cover of the slope.
All the above mentioned processes are described in the book: Schiechtl, H. M. Sicherungsarbeiten im Landschaftsbau, Munich 1973, on pages 135-136, 197-199 and 208, and also in the publication Forschungsgesellschaft fur das Strassenwesen, Arbeitsausschuss Landschaftsgestaltung, 1971; Richtlinien fur den Lebendverbau an Strassen, Cologne, page 30.
Also known are vegetation cores for protection of slopes against erosion described in the Yugoslav patent application P 1595/84. Here, the vegetation core is made as follows: Wire netting is spread on the ground. At appropriate distances, pieces of wire netting are fastened to it. The upper edges of the wire netting are fixed with wire to the wire netting below, making pockets which are filled with earth, turf or other vegetation material. Then, shrubs and small trees and planted into it, forming vegetation cores retaining erosion material.
By such vegetation cores the slope is not perfectly protected against erosion in the initial period of vegetation because the filling material moves at points where there are no vegetation cores.